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Hybrid electric vehicles can be classified according to the way in which power is supplied to the drivetrain:

• In parallel hybrids, the ICE and the electric motor are both connected to the mechanical transmission and can simultaneously transmit power to drive the wheels, usually through a conventional transmission. Honda’s Integrated Motor Assist (IMA) system as found in the Insight, Civic, Accord, as well as the GM Belted Alternator/Starter (BAS Hybrid) system found in the Chevrolet Malibu hybrids are examples of production parallel hybrids.^[19] The internal combustion engine of many parallel hybrids can also act as a generator for supplemental recharging. As of 2013, commercialized parallel hybrids use a full size combustion engine with a single, small (<20 kW) electric motor and small battery pack as the electric motor is designed to supplement the main engine, not to be the sole source of motive power from launch. But after 2015 parallel hybrids with over 50 kW are available, enabling electric driving at moderate acceleration. Parallel hybrids are more efficient than comparable non-hybrid vehicles especially during urban stop-and-go conditions where the electric motor is permitted to contribute,^[19] and during highway operation.

• In series hybrids, only the electric motor drives the drivetrain, and a smaller ICE (also called range extender) works as a generator to power the electric motor or to recharge the batteries. They also usually have a larger battery pack than parallel hybrids, making them more expensive. Once the batteries are low, the small combustion engine can generate power at its optimum settings at all times, making them more efficient in extensive city driving.^[19]

• Power-split hybrids have the benefits of a combination of series and parallel characteristics. As a result, they are more efficient overall, because series hybrids tend to be more efficient at lower speeds and parallel tend to be more efficient at high speeds; however, the cost of power-split hybrid is higher than a pure parallel.^[19] Examples of power-split (referred to by some as “series-parallel”) hybrid powertrains include 2007 models of Ford, General Motors, Lexus, Nissan, and Toyota.^[19][20]

In each of the hybrids above it is common to use regenerative braking to recharge the batteries.

• Full hybrid, sometimes also called a strong hybrid, is a vehicle that can run entirely on its electric motor for a period of time.^[21] Ford‘s hybrid system, Toyota’s Hybrid Synergy Drive, Peugeot-Citroën’s HYbrid4 and General Motors/Chrysler‘s Two-Mode Hybrid technologies are full hybrid systems.^[22] The Toyota Prius, Peugeot 508 RXH HYbrid4, Ford Escape Hybrid, and Ford Fusion Hybrid are examples of full hybrids, as these cars can be moved forward on battery power alone. A large, high-capacity battery pack is needed for battery-only operation. These vehicles have a split power path allowing greater flexibility in the drivetrain by interconverting mechanical and electrical power, at some cost in complexity.
• Mild hybrid, is a vehicle that cannot be driven solely on its electric motor, because the electric motor does not have enough power to propel the vehicle on its own.^[21][22] Mild hybrids include only some of the features found in hybrid technology, and usually achieve limited fuel consumption savings, up to 15 percent in urban driving and 8 to 10 percent overall cycle.^[21][22] A mild hybrid is essentially a conventional vehicle with oversize starter motor, allowing the engine to be turned off whenever the car is coasting, braking, or stopped, yet restart quickly and cleanly. The motor is often mounted between the engine and transmission, taking the place of the torque converter, and is used to supply additional propulsion energy when accelerating. Accessories can continue to run on electrical power while the gasoline engine is off, and as in other hybrid designs, the motor is used for regenerative braking to recapture energy. As compared to full hybrids, mild hybrids have smaller batteries and a smaller, weaker motor/generator, which allows manufacturers to reduce cost and weight.^[22] Honda‘s early hybrids including the first generation Insight used this design,^[22] leveraging their reputation for design of small, efficient gasoline engines; their system is dubbed Integrated Motor Assist (IMA). Starting with the 2006 Civic Hybrid, the IMA system now can propel the vehicle solely on electric power during medium speed cruising. Another example is the 2005–2007 Chevrolet Silverado Hybrid, a full-size pickup truck.^[22] Chevrolet was able to get a 10% improvement on the Silverado’s fuel efficiency by shutting down and restarting the engine on demand and using regenerative braking. General Motors has also used its mild BAS Hybrid technology in other models such as the Saturn Vue Green Line, the Saturn Aura Greenline, the 2008-2009 Chevrolet Malibu Hybrid and the 2013–2014 Chevrolet Malibu Eco.^[22]

A plug-in hybrid electric vehicle (PHEV), also known as a plug-in hybrid, is a hybrid electric vehicle with rechargeable batteries that can be restored to full charge by connecting a plug to an external electric powersource. A PHEV shares the characteristics of both a conventional hybrid electric vehicle, having an electric motor and an internal combustion engine; and of an all-electric vehicle, also having a plug to connect to the electrical grid. PHEVs have a much larger all-electric range as compared to conventional gasoline-electric hybrids, and also eliminate the “range anxiety” associated with all-electric vehicles, because the combustion engine works as a backup when the batteries are depleted.^[21][23][24]

In December 2018, Toyota do Brasil announced the development of the world’s first commercial hybrid electric car with flex-fuel engine capable of running with electricity and ethanol fuel or gasoline. The flexible fuel hybrid technology was developed in partnership with several Brazilian federal universities, and a prototype was tested for six months using a Toyota Prius as development mule.^[25] Toyota announced plans to start series production of a flex hybrid electric car for the Brazilian market in the second half of 2019.^[25][26]

The twelfth generation of the Corolla line-up was launched in Brazil in September 2019, which included an Altis trim with the first version of a flex-fuel hybrid powered by a 1.8-litre Atkinson engine.^[27] By February 2020, sales of the Corolla Altis flex-fuel hybrid represented almost 25% of all Corolla sales in the country.^[28]